The objectives of this work are to design, synthesize, and evaluate hydrocarbon-based or oxygenated hydrocarbon-based CO2 soluble surfactants. These surfactants would be able to form stable water-in-CO2 microemulsions with polar microenvironments capable of dissolving polar species in the bulk non-polar CO2 solvent, or to form metal precursors which can be reduced to nanoparticles in the presence of stabilizing ligands, or to generate foams in-situ for enhanced oil recovery application.
Several oxygenated hydrocarbons, including acetylated sugars, poly(propylene glycol), oligo(vinyl acetate), and highly branched methylated hydrocarbons were used generate CO2-soluble ionic surfactants. Surfactants with vinyl acetate tails yielded the most promising results, exhibiting levels of CO2 solubility comparable to those associated with fluorinated ionic surfactants. For example, a sodium sulfate with single, oligomeric vinyl acetate (VAc) tails consisting of 10 VAc repeat units was 7 wt% soluble in CO2 at 25 oC and 48 MPa. Upon introduction of water to these systems, only surfactants with the oligomeric vinyl acetate tails exhibited spectroscopic evidence of a polar environment that was capable of solubilizing the methyl orange into CO2-rich phase.
Silver bis(3,5,5-trimethyl-1-hexyl) sulfosuccinate, Ag-AOT-TMH, was synthesized from hydrocarbon-based ionic surfactant of sodium bis(3,5,5-trimethyl-1-hexyl) sulfosuccinate, Na-AOT-TMH through ion exchange. Ag-AOT-TMH exhibits 1.2 wt% solubility in dense CO2 at 40 oC and 52 MPa. Silver nanoparticles were produced by reducing the supercritical CO2 solution containing 0.06 wt% Ag-AOT-TMH and 0.5 wt% perfluorooctanethiol (stabilizing ligand) using a reducing agent of NaBH4. Iso-stearic acid, a short, stubby compound with branched, methylated tails, as a hydrocarbon-based nonionic surfactant, has been shown to have high solubility in carbon dioxide. The solvation of the tails by carbon dioxide has made isostearic acid sterically stabilize metallic nanoparticles as a ligand.
The stability of CO2-water emulsion formed by ionic and nonionic surfactants was studied in CO2 at 22 oC and 34.5 MPa for 0.01-1.0 wt% surfactant mixed with equivalent volumes of CO2 and water. Emulsion stability was monitored by observing the rate of collapse of the white, opaque middle-phase emulsion between the transparent CO2 and water phases and the steady-state volume of the emulsion. It was found that at surfactant concentration of 0.01 wt%, oligo(vinyl acetate)10 sodium sulfate displayed the best emulsion, taking over 450 minutes to collapse.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-02092006-121431 |
| Date | 02 June 2006 |
| Creators | Fan, Xin |
| Contributors | J. Karl Johnson, Robert M. Enick, Pradeep P. Fulay, Eric J. Beckman |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-02092006-121431/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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